Twenty-five sows and 265 piglets (Landrace × Yorkshire) were used to evaluate the effects of dietary energy level on the pre-weaning and post-weaning performance of piglets and first parity sows. Sows with an average initial B.W. of 217.54 ± 25.47 kg were randomly assigned to 2 treatments. The treatments consisted of a T1 diet containing 3,100 kcal, and the T2 diet contained 3400 kcal of metabolizable energy (ME)/kg, respectively. Data were analyzed using Duncan statements to test the effect of the dietary energy levels on growth performance in lactating sows and piglets. In this study, Dietary T2 sows had a greater number of weaned piglets per litter (p < 0.05). Dietary T2 had a higher (p < 0.05) body weight than that of T1 in the weanlings, meanwhile it had a higher total average daily gain (p < 0.05) than that of T1. Dietary T1 had a higher average feed intake than that of T2 in gestation and lactation. There were no significant differences on the litter size or litter birth weight. No differences (p > 0.05) were noted in the survival of the piglets as well as in the backfat thickness and body weight loss in sows. In conclusion, these results show that high-energy diets had no effect on the body weight and backfat thickness of sows during gestation and lactation but influenced the body weight and average daily gain of weanling pigs during the lactation period.